Large and medium-sized pulmonary artery obstruction does not play a role of primary importance in the etiology of sickle-cell disease-associated pulmonary hypertension

Background: Pulmonary hypertension (PHT) occurs in approximately 30% of adult patients with sickle-cell disease (SCD) and is a risk factor for early death. The potential role of pulmonary artery obstruction, whether due to emboli or in situ thrombosis, in the etiology of SCD-related PHT is unknown.

Methods: Consecutive SCD patients were screened for PUT (defined as a tricuspid regurgitant jet flow velocity >= 2.5 m/s) employing echocardiography and were evaluated for pulmonary artery obstruction with ventilation-perfusion (VQ) scintigraphy.

Results: Fifty-three HbSS, 6 HbS beta degrees-thalassemia, 20 HbSC, and 6 HbS beta(+)-thalassemia patients were included. The overall prevalence of PHT was 41% in HbSS/HbS beta degrees-thalassemia patients and 13% in HbSC/HbS beta(+)-thalassemia patients. High-probability VQ defects (Prospective Investigation of Pulmonary Embolism Diagnosis criteria) were detected in two patients, one of whom had PUT. In HbSS/HbS beta degrees-thalassemia patients with PHT, 19 patients (86%), 2 patients (9%), and 1 patient (5%) had low-, intermediate-, or high-probability scan results as compared to 30 patients (97%), 1 patient (3%), and 0 patients (0%) in HbSS/HbS beta degrees-thalassemia patients without PHT (p = 0.31). In HbSC/HbS beta(+)-thalassemia patients with PHT, 3 patients (100%), 0 patients (0%), and 0 patients (0%) had low-, intermediate-, and a high-probability scan as compared to 19 patients (90%), 1 patient (5%), and 1 patient (5%) in HbSC/HbS beta(+)-thalassemia patients without PHT (p = 0.86). There were no statistical differences in irregular distribution of the radiopharmaceutical or nonspecific signs associated with PUT between patients with and without PHT.

Conclusions: Although small pulmonary artery obstruction cannot be excluded, large to medium-sized pulmonary artery obstruction is an unlikely primary causative factor in SCD-related PUT.